Electronics > Repair

Sony J30 PSU repair

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Hello everyone,

I am trying to repair an old Sony j30 PSU, which I have no information about or schematics.
I am not an expert in electronics, but I would appreciate some help.
I recapped the whole PSU and still no output, though I get about 15-24v on the power transistors on the primary side. The MC33262 controller gets about 15v.
I get no power on the secondary side.
By the shottcky diode, where I think I have a short, as I replaced the component that seemed to be a diode (white like those connected to the power transistors with no marking on it, or the board itself). but it didn't change anything.
Any idea how to proceed?

Thank you in advance for any help

That is a switch mode power supply.  The "power transistors" on the primary side are working from the rectified 120 Volt AC input stored on that big 150uF capacitor.   Not something that I would advise someone "not an expert in electronics" to be be working on.

I very much appreciate the response and the safety advice. I know enough, I think, to try and repair this board with some help.
As I said the primary side of the board is working as far as I can tell.
I get AC power on the transformer primary side, but not on the secondary. The transformer I refer to is the one, which connects the primary and secondary side of the board – flyback I think is the correct term. Is there a way to test whether the transformer is bad, or the problem is down the secondary side of the board?
Thank you

Dear Joe,

No problem that you don't have circuit diagram. MC33262 is PFC controller. Just open datasheet and you will have information about first stage of
Could you measure votage on the biggest capacitor 150uF@400V. Should be around 380V.

It would probably be a good idea to test those power transistors as they do drive the transformer.


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